This patch allows the user to fault in pages on a virtual cpus
address space for user controlled virtual machines. Typically this
is superfluous because userspace can just create a mapping and
let the kernel's page fault logic take are of it. There is one
exception: SIE won't start if the lowcore is not present. Normally
the kernel takes care of this [handle_validity() in
arch/s390/kvm/intercept.c] but since the kernel does not handle
intercepts for user controlled virtual machines, userspace needs to
be able to handle this condition.
Signed-off-by: Carsten Otte <cotte@xxxxxxxxxx>
---
---
arch/s390/kvm/kvm-s390.c | 6 ++++++
include/linux/kvm.h | 1 +
2 files changed, 7 insertions(+)
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -777,6 +777,12 @@ long kvm_arch_vcpu_ioctl(struct file *fi
break;
}
#endif
+ case KVM_S390_VCPU_FAULT: {
+ r = gmap_fault(arg, vcpu->arch.gmap);
+ if (!IS_ERR_VALUE(r))
+ r = 0;
+ break;
+ }
default:
r = -EINVAL;
}
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -669,6 +669,7 @@ struct kvm_s390_ucas_mapping {
#define KVM_S390_ENABLE_UCONTROL _IO(KVMIO, 0x49)
#define KVM_S390_UCAS_MAP _IOW(KVMIO, 0x50, struct kvm_s390_ucas_mapping)
#define KVM_S390_UCAS_UNMAP _IOW(KVMIO, 0x51, struct kvm_s390_ucas_mapping)
+#define KVM_S390_VCPU_FAULT _IOW(KVMIO, 0x52, unsigned long)
/* Device model IOC */
#define KVM_CREATE_IRQCHIP _IO(KVMIO, 0x60)
--
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